[tex]\text{Media aritmetica a doua numere este semisuma acelor numere.}\\
\text{Altfel spus:}m_{a,b}=\dfrac{a+b}{2}\\
\text{Pnetru exercitiul de fata vom avea:}\\
m_{a,b}=\dfrac{\dfrac{1}{11}+\dfrac{1}{12}+_{\dots}+\dfrac{1}{2000}+\dfrac{10}{11}+\dfrac{11}{12}+_{\dots}+\dfrac{1999}{2000}}{2}\\
m_{a,b}=\dfrac{\left(\dfrac{1}{11}+\dfrac{10}{11}\right)+\left(\dfrac{1}{12}+\dfrac{11}{12}\right)+_{\dots}+\left(\dfrac{1}{2000}+\dfrac{1999}{2000}\right)}{2}\\
[/tex]
[tex]~~~~~~~~~~~~~de\ 1990\ ori\\
m_{a,b}=\dfrac{\overbrace{1+1+1+1+1}}{2}\\
m_{a,b}=\dfrac{1990}{2}=\boxed{995}[/tex]
